#coding=utf-8
import lxml.html as HTML
from pyquery import PyQuery as pq
import urllib2
import urlparse
import re
content = urllib2.urlopen('http://www.douban.com/group/topic/35481511/').read().decode('utf-8')
tt = pq(content)
print urlparse.urljoin('http://www.douban.com/',tt('iframe').attr('src'))